When a human is orally infected with a human norovirus, the virus proliferates in the duodenum and the upper portion of the small intestine, thereby triggering infectious gastroenteritis. In this case, epithelial cells of the small intestine near the duodenum fall, thereby causing symptoms including vomiting, diarrhea, and abdominal pain. The incubation period from infection with norovirus to the onset is about 12 hours to 72 hours (average 1 to 2 days), and excretion of the virus to the feces lasts about 1 to 3 weeks even after the symptoms have disappeared. In some cases, such virus excretion for longer than 7 weeks is reported. About 70% of reported cases of food poisoning are caused by norovirus infection.
A norovirus is a virus having no envelope and having a plus single-stranded RNA of about 7,500 bases as the genome thereof. The genome of the norovirus is reported to include three protein coding regions (ORFs): ORF1, coding for a non-structural protein relating to viral replication; ORF2, coding for a capsid structural protein (VP1); and ORF3, coding for a minor structural protein (VP2). Also, the norovirus is categorized into 5 groups: Genogroups I to V (GI to GV), on the basis of similarity of capsid gene sequence. Of these, noroviruses GI, GII, and GIV are main causal viruses for human infection. In particular, Genogroup I (GI) and Genogroup II (GII) have a genetic diversity, and a variety of viruses having different phylogenetic properties are detected in specimens from humans. Thus, Genogroup I and Genogroup II may be divided into 14 or more genotypes and 17 or more genotypes, respectively.
Detection of norovirus is carried out by detecting a capsid structural protein with an antibody through enzyme immunoassay (EIA) (see Non-Patent Document 1) or immunochromatography (Non-Patent Document 2). Thus, correct detection of a human norovirus antigen requires an antibody that responds to all the genotypes.
However, hitherto, an antibody that can recognize and respond to a common antigen region has not been readily obtained. Thus, a norovirus detection reagent is produced through combination of a plurality of antibodies to norovirus antigen peptides having a specific amino acid sequence or to fragments thereof (see, for example, Patent Document 1), and noroviruses of different genotypes are individually detected.
Therefore, there is demand for creating an antibody that can comprehensively detect a wide variety of noroviruses GII of different genotypes.